1. Field of the Invention
The present invention is related to a semiconductor integrated circuit device of ASICs etc., and a power supply routing method and system for improving the layout of wiring configuration.
2. Prior Art
As power supply wiring structures of conventional integrated circuits, 3 kinds are generally known, i.e., (1) structures with varied widths of wiring, (2) structures with power supply auxiliary wiring that electrically reinforces the main power supply wiring, (3) structures with the ring-shaped power supply main wiring within which optional form power supply auxiliary wiring.
FIG. 1 is a schematic diagram showing the example of a power supply wiring structure of the above (1) that was disclosed in Japanese Published Application No.Hei2-188,943. In the same figure, the reference numeral 100a.about.100f are function blocks of a LSI chip and the reference numeral 101,102 is a first layer power supply wiring. Also, the reference numeral 103 is a second layer power supply wiring and the reference numeral 104 is a power supply pad.
The design method of the power supply wiring is conducted first by calculating consumption of electric power within each of the function blocks, which are spatially defined by the power supply wiring to be provided. Then, the wiring width of the power supply wiring is determined on the basis of the calculation result of the electric power consumption.
The effective average electric current supplied to each of the function blocks is calculated, on the assumption that the current is passed from the power supply pad 104 through the first layer power supply wiring 101,102 and a via 105 in the example, and therefore the wiring widths of the second layer power supply wiring 103a, 103b are 2 times wider than others.
FIG. 2 shows the examples of the power supply wiring structure of the above (2) that was shown in Japanese Published Application No.Hei2-187,050. In the same figure, the reference numerals 201,202 are power supply wirings, 203,204 are power supply auxiliary wirings, and 205 is a basic cell composed of a plural transistor. The power supply auxiliary wiring 208 is arranged in the column direction for each m cells of the basic cell 205 while the power supply auxiliary wiring 204 is arranged in the line direction for each m cells of the basic cell 205. The arrangement process of this power supply auxiliary wiring 203,204 determines with the wiring width and the wiring interval in order to optimally control the electric current density inside the area as defined by the power supply auxiliary wiring 203,204.
FIG. 3 is the figure that shows the examples of the power supply wiring structure of the above (3) that was shown in Japanese Published Application No.Hei4-107,845. In the same figure, the reference numeral 301 is a function block, the reference numeral 302 is an electric current source, the reference numeral 803 is the ring-shaped power supply wiring and also 304 is a power supply pad. An optional form power supply wiring is connected to the ring-shaped power supply wiring 303 within each function block 201. Electric power is supplied to the electric current source 302 through the power supply wiring inside the ring-shaped power supply wiring 303 and also the function block 301 from the power supply pad 304.
However, there are the following problems in the above conventional power supply wiring structure. While electric power (electric current) consumption increases with a larger scale integration, conventional structures such as those composed only with usual power supply wiring e.g., ring-shaped power supply wiring with the varied wiring width of (1) mentioned above and the structure that established optional form power supply wiring inside of the basic ring-shaped power supply wiring tend to result in a wrong action originating from fluctuation of the power supply voltage due to voltage drop and poor performance which can not satisfy the required specification.
In the case of the structure having the power supply auxiliary wiring that electrically reinforces main power supply wiring in which voltage drop is mitigated by the power supply auxiliary wiring, there is the possibility that the sufficient voltage is not obtained because wiring width and wiring interval etc. are calculated based upon the consumption electric power inside only the small area as divided, without considering that electric current flows to the areas which are out of consideration when the power supply auxiliary wiring is designed. Furthermore there are many wastes in the wiring resources, because the power supply auxiliary wiring is arranged in many areas where the voltage drop is not so large as to require the power supply auxiliary wiring.